1. Technical Field
This disclosure relates to a solder recovery device which recovers a recycled solder from solder dross.
2. Description of the Related Art
When a flow soldering process is carried out, a solder comes into contact with oxygen, and thus, solder dross is inevitably generated. The generation of solder dross is higher in a Sn—Ag—Cu alloy, which is a mainstream Pb-free solder, than in a Sn—Pb solder, which has been widely used in recent years.
The solder dross contains a usable recycled solder, and oxidized residue, which should be disposed. A technique which recycles such solder dross as a usable recycled solder is known. However, with a conventional method of removing oxidized residue from solder dross, the oxidized residue can not be completely removed, and the oxidized residue which should be disposed still contains the recycled solder.
A common conventional method of recovering a solder involves separating solder dross up and down into a recycled solder and oxidized residue by heating the solder dross and agitating the heated solder dross, and then collecting the recycled solder after an operator has removed the upper oxidized residue with a ladle.
However, this solder recovering method not only removes the oxidized residue but also collects the recycled solder when removing the oxidized residue. Therefore, there is a problem in that the amount of residual solder in the oxidized residue is large.
There is also a problem in that the operation efficiency is deteriorated because it is necessary to carefully conduct a recovering operation such that the recycled solder does not mix with the oxidized residue. In addition, there is a problem in that effects on the body are a concern from a safety standpoint because the operation for removing the oxidized residue with a ladle is an operation in dusty environment.
Consequently, as described in JP3733362B, JP2005-344204A and JP2004-311620A, a method of effectively recovering a recycled solder without being mixed with oxidized residue is proposed.
For example, in the device described in JP3733362B, after melting solder dross in a melting crucible, the melted solder dross is first-screened for the purpose of improving the solder recovery rate. When the solder dross is first-screened, the recycled solder is coagulated into droplet form or is linearly coagulated, and the oxidized residue is cooled down to a powdery state. The recycled solder obtained by the first screening is second-screened, such that the powdery oxidized residue is removed from the recycled solder.
In the device described in JP2005-344204A, the solder dross is separated into the recycled solder and the oxidized residue by hydrovolcanic-exploding the solder dross. After the separation, the recycled solder and the oxidized residue are centrifuged, and the recycled solder is recovered in a particle state.
In the device described in JP2004-311620A, solder dross is agitated in a semispherical melting crucible, and is separated into a recycled solder and oxidized residue. After the separation, the recycled solder is flowed into an ingot provided in the lowest portion of the semispherical melting crucible from the bottom portion of the semispherical melting crucible.
However, in the device described in JP3733362B, the solder which is downsized in a droplet-like form by the first screening may pass through the second screening. Moreover, the small droplet-like solder may be destroyed.
Furthermore, after the first screening, the powdery oxidized residue may remain inside a solder, and the recycled solder may be coagulated in that state. When the coagulated recycled solder is second-screened, the oxidized residue which is adhered around the recycled solder can be removed, but the oxidized residue remaining inside the solder can not be removed.
In the device described in JP2005-344204A, when sucking up solder dross, the solder is coagulated while containing oxidized residue, and the oxidized residue on the surface may be removed, but the oxidized residue remaining inside the solder may not be removed.
If the device includes functions such as hydrovolcanic explosion and centrifugal separation, the device becomes complex, resulting in the increase in the costs. Even if the hydrovolcanic explosion is small, such hydrovolcanic explosion has a problem from a safety standpoint.
The device described in JP2004-311620A is suitable for recovering only a recycled solder, but the recycled solder may remain in the oxidized residue which should be disposed. When disposing the oxidized residue, the separated recycled solder may be mixed with the solder remaining in the oxidized residue, and the mixed solder may remain in the oxidized residue, so that the residual volume of the solder in the oxidized residue may not be reduced.